Tove is a young girl who lives high in the mountains with her grieving father and her imaginative little brother Lars, caring for the family since their mother's death. One night their home is attacked by a pitch-black creature straight out of an old fairy tale, and Lars is snatched away and dragged through a portal into an enchanted, snowbound wilderness. Refusing to give up, Tove sets off alone into the ancient forest, where she meets strange folklore creatures and unravels the mysteries of the land as she searches for a way to reach her brother and bring him home.